472,363 Members | 2,039 Online

# Pattern Matching Over Python Lists

Is anyone aware of any prior work done with searching or matching a
pattern over nested Python lists? I have this problem where I have a
list like:

[1, 2, [1, 2, [1, 7], 9, 9], 10]

and I'd like to search for the pattern [1, 2, ANY] so that is returns:

[1, 2, [1, 2, [6, 7], 9, 9], 10]
[1, 2, [6, 7], 9, 9]
Jun 27 '08 #1
9 4228
At 2008-06-17T05:55:52Z, Chris <ch*******@gmail.comwrites:
Is anyone aware of any prior work done with searching or matching a
pattern over nested Python lists? I have this problem where I have a
list like:

[1, 2, [1, 2, [1, 7], 9, 9], 10]

and I'd like to search for the pattern [1, 2, ANY] so that is returns:

[1, 2, [1, 2, [6, 7], 9, 9], 10]
[1, 2, [6, 7], 9, 9]
Hint: recursion. Your general algorithm will be something like:

def compare(list, function):
if function(list):
print list
for item in list:
if item is a list:
compare(item, function)

def check(list):
if list starts with [1, 2] and length of the list 2:
return True
else:
return False
--
Kirk Strauser
The Day Companies
Jun 27 '08 #2
Kirk Strauser:
Hint: recursion. Your general algorithm will be something like:
Another solution is to use a better (different) language, that has
built-in pattern matching, or allows to create one.

Bye,
bearophile
Jun 27 '08 #3
Thanks for your help. Those weren't quite what I was looking for, but
I ended up figuring it out on my own. Turns out you can actually
search nested Python lists using simple regular expressions.
Jun 27 '08 #4
On Jun 17, 1:09 pm, bearophileH...@lycos.com wrote:
Kirk Strauser:
Hint: recursion. Your general algorithm will be something like:

Another solution is to use a better (different) language, that has
built-in pattern matching, or allows to create one.

Bye,
bearophile
Btw, Python's stdlib includes a regular expression library. I'm not
sure if you're trolling or simply unaware of it, but I've found it
Jun 27 '08 #5
On Jun 20, 10:45 am, Chris <chriss...@gmail.comwrote:
On Jun 17, 1:09 pm, bearophileH...@lycos.com wrote:
Kirk Strauser:
Hint: recursion. Your general algorithm will be something like:
Another solution is to use a better (different) language, that has
built-in pattern matching, or allows to create one.
Bye,
bearophile

Btw, Python's stdlib includes a regular expression library. I'm not
sure if you're trolling or simply unaware of it, but I've found it
Kindly consider a third possibility: bearophile is an experienced
Python user, has not to my knowledge exhibited any troll-like
behaviour in the past, and given that you seem to be happy using the
re module not on strings but on lists of integers, may have been
wondering whether *you* were trolling or just plain confused but just
too polite to wonder out loud :-)
Jun 27 '08 #6
On Jun 20, 1:44*am, Chris <chriss...@gmail.comwrote:
Thanks for your help. Those weren't quite what I was looking for, but
I ended up figuring it out on my own. Turns out you can actually
search nested Python lists using simple regular expressions.
Strange?
How do you match nested '[' ... ']' brackets?

Jun 27 '08 #7
On Jun 20, 1:45*am, Chris <chriss...@gmail.comwrote:
On Jun 17, 1:09 pm, bearophileH...@lycos.com wrote:
Kirk Strauser:
Hint: recursion. *Your general algorithm will be something like:
Another solution is to use a better (different) language, that has
built-in pattern matching, or allows to create one.
Bye,
bearophile

Btw, Python's stdlib includes a regular expression library. I'm not
sure if you're trolling or simply unaware of it, but I've found it
bearophile was talking about matching lists and tuples, not matching
strings.

Python's regular expression module works with characters in strings,
but the same approach can be applied to items in lists and tuples.
Jun 27 '08 #8
On Jun 19, 9:03 pm, John Machin <sjmac...@lexicon.netwrote:
On Jun 20, 10:45 am, Chris <chriss...@gmail.comwrote:
On Jun 17, 1:09 pm, bearophileH...@lycos.com wrote:
Kirk Strauser:
Hint: recursion. Your general algorithm will be something like:
Another solution is to use a better (different) language, that has
built-in pattern matching, or allows to create one.
Bye,
bearophile
Btw, Python's stdlib includes a regular expression library. I'm not
sure if you're trolling or simply unaware of it, but I've found it

Kindly consider a third possibility: bearophile is an experienced
Python user, has not to my knowledge exhibited any troll-like
behaviour in the past, and given that you seem to be happy using the
re module not on strings but on lists of integers, may have been
wondering whether *you* were trolling or just plain confused but just
too polite to wonder out loud :-)
Fair enough. To help you understand the method I used, I'll give you
this hint. It's true that regex on works on strings. However, is there
any way to convert arbitrarily complex data structures to string
representations? You don't need to be an experienced Python user to
Jun 27 '08 #9
Fair enough. To help you understand the method I used, I'll give you
this hint. It's true that regex on works on strings. However, is there
any way to convert arbitrarily complex data structures to string
representations? You don't need to be an experienced Python user to
match nested parenthesis, so I think your method will have a problem
with nested lists, unless your actual inputs are much simpler than the
general case.

Eli
Jun 27 '08 #10

This thread has been closed and replies have been disabled. Please start a new discussion.

### Similar topics

 2 by: BalyanM | last post by: Hi, I am new to python.I am using it on redhat linux 9. I am interested to run python on a sun machine(SunE420R,os=solaris) with 4 cpu's for a pattern discovery/search program on biological... 176 by: Thomas Reichelt | last post by: Moin, short question: is there any language combining the syntax, flexibility and great programming experience of Python with static typing? Is there a project to add static typing to Python? ... 3 by: Greg Lindstrom | last post by: Hello- I'm running Python 2.2.3 on Windows XP "Professional" and am reading a file wit 1 very long line of text (the line consists of multiple records with no cr/lf). What I would like to do is... 9 by: Xah Lee | last post by: # -*- coding: utf-8 -*- # Python # Matching string patterns # # Sometimes you want to know if a string is of # particular pattern. Let's say in your website # you have converted all images... 4 by: Xah Lee | last post by: 20050207 text pattern matching # -*- coding: utf-8 -*- # Python # suppose you want to replace all strings of the form # # to #